Disposable absorbent products, such as diapers, training pants, incontinence articles typically include stretchable materials, such as elastic strands, in the waist region and the cuff regions to provide a snug fit and a good seal of the article. Pant-type absorbent articles further include stretchable materials in the side portions for easy application and removal of the article and for sustained fit of the article. Stretchable materials have also been used in the ear portions for adjustable fit of the article.
There are various approaches to provide desirable elastic properties in those areas. Stretchable materials may be films or nonwoven fibrous webs made of elastomeric materials. Typically, such materials are stretchable in any direction. However, because the films or webs are made entirely of elastomeric materials, they are relatively expensive, and they tend to have more drag on skin surface, resulting in discomforts to the wearer of the article. Sometimes, the stretchable films are laminated to one or more layers of nonwoven webs. Since typical nonwoven webs typically are made of thermoplastic fibers, they have very limited stretchability and, the resulting laminates provide considerable resistance to stretch. It is necessary to reduce this resistance substantially in order to make functional stretch laminates.
Other approaches to make stretchable materials are also known, including: stretch-bonded laminates (SBL) and necked-bonded laminates (NBL). Stretch bonded laminates are made by stretching the elastic strands in the machine direction (MD), laminating it to one or more nonwoven substrates while it is in the stretched state, and releasing the tension in the elastic strands so that the nonwovens gather and take on a puckered shape. Necked-bonded laminates are made by first stretching the nonwoven substrate in the machine direction such that it necks (i.e., reduces its dimension) at least in the cross machine direction (CD), then bonding the elastic strands to the substrate while the substrate is still in the stretched, necked state. This laminate will be stretchable in CD, at least up to the original width of the nonwoven before it was necked. Combinations of stretch bondings and neck bondings have also been known to deliver stretch in both MD and CD direction. In these approaches, at least one of the components is in a tensioned (i.e., stretched) state when the components of the laminates are joined wherein.
Zero strain stretch laminates are also known. The zero strain stretch laminates are made by bonding the elastomer to the nonwoven while both are in an unstrained state. The laminates are then incrementally stretched to impart the stretch properties. The incrementally stretched laminates are stretchable only to the extent afforded by the non-recovered (i.e., residual) extensibility of the laminate. For example, U.S. Pat. No. 5,156,793, issued to Buell et al., discloses a method for incrementally stretching the elastomer-nonwoven laminate web, in a non-uniform manner, to impart elasticity to the resulting laminate.
In all the approaches above, stretch laminates are made separately. The stretch laminates must be cut into the appropriate size and shape, then adhesively attached to the desired location in the product in a process sometimes referred as the “cut-and-slip” process. Because of the different stretch properties required for different elements of the product, it is necessary to make a variety of laminates having different stretchability and cut the laminates to different sizes and shapes. Several cut and slip units may be needed to handle the different stretchability of the stretch laminates and to attach them to different locations of the product. As the number of cut-and-slip units and/or steps multiplies, the process quickly becomes cumbersome and complicated.
Based on the foregoing, it is desirable to have a cost effective stretch composite having elastomeric materials disposed only in specific areas in specific amount for stretchability. It is also desirable to have a stretch composite having variable stretchabilities among discrete, spaced apart elements of the article. It is further desirable to have stretch composites having variable stretchability locally (i.e., within an element of the article).
Moreover, it is desirable to have a cost effective process that does not involve multi-steps and/or multi-units and that delivers variable stretch properties to various portions of the absorbent article. Such process for making the above variable stretch composites is desirable because it has total flexibility that allows for controlled deposition of different types and/or amount of elastomeric materials where they are needed. Such process is also desirable because it tailors the delivery of stretchability and resistance to stretch in various portions of a product to deliver improved fit and comfort to the wearer.